denormalization_with_arrays.rb

require_relative "activerecord_setup"

ActiveRecord::Schema.define do
  create_table :foos, force: true do |t|
    t.jsonb :bar_links

    t.timestamps
  end

  create_table :bars, force: true do |t|
    t.timestamps
  end

end

module DenormalizedAssociations
  def denormalized_has_many(associated_table_name)
    define_method associated_table_name do
      associated_table_name.
        to_s.
        classify.
        constantize.
        where(
          id: send("#{associated_table_name.to_s.singularize}_links").map do |link|
            link["id"]
          end
        )
    end

    define_method "#{associated_table_name.to_s.singularize}_ids" do
      send("#{associated_table_name.to_s.singularize}_links").map do |link|
        link["id"]
      end
    end
  end
end

class ActiveRecord::Base
  extend DenormalizedAssociations
end

class Foo < ActiveRecord::Base
  denormalized_has_many :bars
end

class Bar < ActiveRecord::Base
end

class DenormalizationTest < Minitest::Test
  def setup
    Foo.destroy_all
    Bar.destroy_all
  end

  def test_has_many
    5.times do
      Bar.create
    end

    foo = Foo.create(
      bar_links: [
        { id: 1, fruit: "banana" },
        { id: 2, fruit: "orange" }
      ]
    )

    assert_equal(foo.bars.map(&:id), [1, 2])
    assert_equal(foo.bar_ids, [1, 2])
  end

  def test_querying
    5.times do
      Bar.create
    end

    foo = Foo.create(
      bar_links: [
        { id: 1, fruit: "banana" },
        { id: 2, fruit: "orange" }
      ]
    )

    2.times do
      Foo.create(
        bar_links: [
          { id: 3, fruit: "pear" }
        ]
      )
    end

    assert_equal(
      [ foo ],
      Foo.where("bar_links @> '[{\"id\": 1}]'")
    )
  end
end